Phase shifting device



Dec. 25, 1956 P. l. CORBELL PHASE SHIFTING DEVICE 2 Sheets-Sheei;

Filed Dec. 10, 1952 A I) 5 8 p s 4 m 6 3 WP, .H w w m L Q r J 6 w L 5 YD INVENTOR. P4041 (o/Pail;

147 r a/im [y Dec. 25, 1956 P. l. CORBELL PHASE SHIFTING DEVICE 2Sheets-Sheet 2 Filed Dec. 10, 1952 INVENTOR. I240 Canwuzl.

A T ran/v17 PHASE SHIFTING DEVICE Paul I. Corbell, Palo Alto, Calif.,assignor, by mesne assignments, to the United States of America asrepresented by the United States Atomic Energy Commission ApplicationDecember 10, 1952, Serial No. 325,155

5 Claims- (Cl. 333-31) This invention relates in general to a phaseshifting device, and in particular to means for shifting phase atmicrowave frequencies.

In transmission line systems, it is oftentimes necessary to change thephase of transmitted energy before it is received at the end of theline. At relatively low frequencies, phase shifting can be accomplishedby using lumped reactive elements in shunt with the line. In general soas to obtain the desired ratio of voltage to current at the end of theline, additional 'reactiveelements are required.

' Patented "Dec; 25,-"1956 2 of legs 21 and 22, respectively, and a topframe member 23.

As best shown in Figure 2, the top frame member 23 is formed with anextension 24 which supports a bracket 26 upon which a driving means 27,as for example an electric motor, is supported. v

A jack 28 is attached to the member 23 and supports a longitudinalmember 29. A jack screw 31 controls the position of the jack 28 and isconnected to the motor 27 by means of gears 32 and 33, universals 34 and36, and

a slide shaft 37.

Supported from the member 29 are a pair of dielectric probes 38 and 39which are attached to hangers 41 and 42 connected to the support 29. Thehangers 41 and 42 are connected by suitable clamps 43 and 44 to theprobes 38 and 39.

The probes 38 and 39 extend within the confines of the wave guide 10 andpass through openings 46 and 47,

respectively, formed in the top wall 11. Guide members 48 and 49 areattached to the top wall 11 in alignment with the openings 46 and 47 andthe probes 38 and 39 pass therethrough as shown in detail in Figure 3.

At high radio frequencies (short wave lengths) where a phase shift ofmany electrical degrees occurs in a relatively short length oftransmission line, it is possible to devise means for physicallyaltering the length of the line so as to produce the desired amount ofphase delay. Such arrangements are called line stretchers.

In high frequency lines it is also possible to introduce reactance inshunt with the line by using transmission line stubs, and thus obtainphase delay.

At microwave frequencies it becomes difiicult to mechanically build aline stretcher and generally shunt impedances are inserted into the lineto obtain the desired phase shift. Such impedances may be in the form ofdielectric wedges, such as described in Ragan Microwave TransmissionSystem, volume 9, MIT series, published by McGraw-Hill.

l t is an object of the present invention to provide phase shift atmicrowave frequencies by inserting into wave guides, dielectric probescausing a resultant capacity and shunt across the line.

Another object of the present invention is to provide a phase shiftingdevice for microwave frequencies which will not cause reflection orcontinuity.

Yet another object of the present invention is to control the phaseshift in a microwave guide.

A feature of the present invention is found in the provision for theinsertion of a pair of dielectric rods into the plane of the maximumvoltage lines in a wave guide with the probes separated one-quarter wavelength so as to cancel reflections.

Further features, objects and advantages of this invention will becomeapparent from the following description and claims when read in view ofthe drawings, in which:

Figure 1 is a sectional view of a wave guide with the apparatus of thisinvention installed therein;

Figure 2 is a side view of the phase shifting apparatus of thisinvention; and

Figures 3, 4, and 5 are detailed sectional views of various embodimentsof the dielectric probe of this invention.

Figure 1 illustrates a wave guide designated generally as 19 which hasupper and lower conducting walls 11 and 12 and side walls 13 and 14,respectively. A pair of brackets 16 and 17 which might, for example, beangle irons are attached to the upper surface 11 of the wave guide andsupport a pair of U-shaped frame members 18 and 19. The members 18 and19 are formed with a pair With the structure thus shown, the verticalpositions of the probes 38 and 39 may be controlled together.

The probes 38 and 39 are made of dielectric material so that energypassing down the wave guide will be rotated in phaseby them. Variousmaterials may be .used for the probes 38 and 39, as for example, ceramicrods, hollow glass rods filled with oil, hollow glass rods filled withwater, and glass rods filled with dielectric powder. When rods arefilled with dielectric powder as shown in Figure 4, the powder in bothrods may be similarly compressed to a multitude of densities to vary theeffective dielectric constant. Figure 3 illustrates a solid plastic orceramic dielectric rod. Figure 4 illustrates a hollow glass tube filledwith dielectric powder. Figure 5 illustrates a hollow glass tube filledwith a liquid dielectric.

Applicant has also found that the probes shown in Figure 2 worksatisfactorily wherein a glass tube has its bottom end closed and itsupper end closed by a stopper 51 through which a pair of tubes 52 and 53extend. The tube 53 extends adjacent the bottom of the probe and tube 52terminates adjacent the stopper 51. If water or other suitabledielectric liquid is fed into the tube 53, it will emerge adjacent thebottom of the tube and force the other liquid up and out of the tube 52.

It is to be realized, of course, that a certain amount of energy isabsorbed by the probes, resulting in heating of the probes. Thus,circulation of liquid keeps the bottom ends of the probes at a safeoperating temperature.

A pair of probes 38 and 39 are used and are spaced one-quarterguide-wave length apart so as to cancel reflections, caused by theprobes. It is well known that discontinuities encountered by energypassing through a Wave guide cause reflections and if a pair of similarobjects are inserted into the guide and spaced one-quarter wave lengthsapart, these reflections will cancel.

A particular embodiment constructed by applicant was designed for 202.5megacycles wherein the air wave length is approximately 60 inches. Waveguide was used with the sides 11 and 12 being 48 inches long and thesides 13 and 14 being 12 inches high. With this wave guide, the wavelength is 84 inches and one-quarter wave length is 24 inches. Thus, theprobes 38 and 39 were separated 24 inches.

With probes one and a half inches in diameter and using water as thedielectric, phase rotations up to 25 degrees were obtained with the twoprobes. It is to be realized, of course, that the phase rotation dependsupon the length of the probes within the wave guide.

It is seen that this invention provides a novel way for rotating thephase of energy passing down a relatively large wave guide in a mannersuch that no reflections occur.

Although this invention has been described with respect to a particularembodiment thereof, it is not to be so limited as changes andmodifications may be made which are within the full intended scope ofthe invention, as defined by the appended claims.

I claim:

1. Means for adjusting the phase of energy traveling down a wave guidecomprising, a pair of openings formed in a wide side of said wave guide,a pair of probes extending through said openings and separatedlongitudinally of said wave guide by substantially one-quarter wavelength, and said probes comprising generally hollow cylindrical tubeswith their lower ends closed, closure means mounted in the other ends ofsaid tubes, a pair of openings formed in each of said closure means, anda separate pair of smaller tubes extending through the openings of eachof said closure means with one of said smaller tubes of each pairextending further into its respective probe than the other.-

2, Means vfor changing the efiective length of a waveguide withoutcausing substantial reflection of energy comprising, a first dielectricprobe comprising a hollow dielectric container of a fixed geometricalform containing at least one dielectric material which is incapable ofmaintaining a fixed geometrical form by itself, said probe beinginserted through an opening in said waveguide, a second dielectric probeidentical with said first probe inserted through another opening in saidwaveguide, said probes longitudinally spaced one-quarter wavelengthapart, a pair of guide members mounted on the outside of said waveguidein alignment with said openings to guide said probes into alignment withsaid openings, jack means supported on the outside of said waveguide, alongitudinal member supported by said jack means, and hanger meansmounted from said longitudinal member and supporting said probes so thatsaid probes are adjustable together into said waveguide by said jackmeans.

3. A device as in claim 2 wherein said probes are glass tubes sealed attheir bottom ends, a stopper mounted in the upper end of each probe andformed with a pair of openings, a pair of small tubes supported throughthe openings in each stopper with the portion of one tube Within theprobes being substantially longer than the equivalent portion of theother, and a dielectric material other than glass contained within eachof said probes.

4. A device as in claim 2 wherein a dielectric powder is containedwithin each probe.

5 A device as in claim 2 wherein said probes are glass tubes sealed atone end, a stopper mounted in the other end of each probe and formedwith a pair of openings, a pair of small tubes supported through theopenings in each stopper, with the portion of one tube which is withinthe probes being substantially longer than the other and a dielectricfluid contained within each of said probes.

References Cited in the file of this patent UNITED STATES PATENTS2,556,001 Robertson June 5, 1951 2,605,413 Alvarez July 29, 19522,705,307 Nyswander Mar. 29, 1955

